1. Field of the Invention
This invention relates to a power dividing transmission system adapted to transmit mechanical power in a stepless speed change manner. Said system comprises a driving part; a driven part; at least one stepless speed change transmission device adapted to vary the speed ratio of said system and a mechanism with degree of freedom greater than one, called Multi-freedom mechanism, having moving parts respectively connected to said driving part, driven part and the drive parts of said device.
The degree of freedom of the transmission system as described herein is the freedom when the frame thereof is in fixed state.
ln the present invention, where it is mentioned that two moving parts are connected means that there is a fixed speed ratio between the two parts e.g., two shafts are coupled together or one gear is engaged to another.
The speed ratio of a transmission system in the present invention is the kinetic parameter ratio of the driving part to the driven part of the said system, i.e. EQU i.sub.12 =n.sub.1 /n.sub.2
where
i.sub.12 is the speed ratio of the so said system,
n.sub.1 is the angular displacement or rotating speed of the driving part, and
n.sub.2 is the kinetic parameter of the driven part, in the same unit as n.sub.1.
2. Description of the Prior Art
In the aforesaid system, any said stepless speed change device that the change of speed ratio thereof will vary the speed ratio of the system is called a regulating device of the system, and the moving parts of the multi-freedom mechanism connected to said regulating device are called adjusted parts of said device.
In operation, the power is transmitted through not only said multi-freedom mechanism but also through the said regulating device. The power transmitted by said regulating device is called branch power.
Generally, the multi-freedom mechanism of a transmission system employs a gear train comprising epicyclic gear trains or other similar differential mechanism. The speed regulating device of said system may be a hydrodynamic torque converter, fluid coupling magnetic slip clutch, frictional stepless speed change device, hydraulic stepless speed change device or combination composed of any aforesaid device and other mechanisms.
Usually, the efficiency of the multi-freedom mechanism is very high and the life of service longer, while the efficiency of the speed regulating device is lower and life of service shorter. With more branch power, the transmission system requires a regulatinq device with greater capacity and the performance of such transmission system deteriorates. Accordingly, one area of improvement for existing power dividing stepless speed change transmissions is the reduction of its branch power.